Optical Disc Tracking Control Stabilization Awaiting Process
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Solution Overview
Problem
Optical disc devices face challenges in fine-tuning the value of K in the differential push-pull method for effective tracking control, leading to variations in tracking-error signals due to lens oscillations, especially with discs having offset centers of gravity.
Innovation Solution
The optical disc device incorporates a control unit that performs a stabilization awaiting process to reduce lens oscillation, allowing for precise adjustment of the K value by measuring tracking-error signals after the oscillation has stabilized, using either a fixed time or amplitude-based criteria, and adjusts the offset value accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the value of K is adjusted immediately after lens movement without waiting for oscillation stabilization, then the adjustment process is faster, but the measurement precision of the tracking-error signal deteriorates due to lens oscillation
Solution Approach 1:
The patent applies preliminary action by performing the stabilization awaiting process before measuring the tracking-error signal. The control unit waits for a predetermined period after lens movement to allow oscillation to subside before proceeding with the measurement and K value adjustment. This ensures that measurements are taken when the lens is relatively stable, improving measurement precision without significantly extending the overall adjustment time.
2Measurement precision
If the stabilization awaiting process waits for complete oscillation stabilization, then the measurement precision improves, but the loss of time increases
Solution Approach 1:
The patent applies partial action by implementing a predetermined stabilization period that does not require complete oscillation cessation. Instead of waiting for total stabilization, the control unit waits for a fixed period sufficient to reduce oscillation to an acceptable level, then proceeds with measurement. This balances measurement precision requirements with time efficiency.
3Device complexity
If the offset value is adjusted without considering lens oscillation, then the adjustment process is simpler, but the reliability of tracking control deteriorates
Solution Approach 1:
The patent applies preliminary action by incorporating the stabilization awaiting process before offset value adjustment. The control unit waits for lens oscillation to subside before measuring the tracking-error signal and determining the optimal offset value. This simple temporal separation ensures reliable measurements and accurate offset adjustment without adding complex oscillation detection or compensation mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the variation in the adjusted value of K, enhancing the stability and accuracy of tracking control in optical disc devices, particularly for discs with significant lens oscillations.
Implementation Method 1
an objective lens which focuses a laser light from a predetermined light source on any position on an optical disc
Implementation Method 2
a receiver unit configured to receive light reflected off the optical disc
Data Source
AI summary
Provided is an optical disc device including: an optical pickup which includes an objective lens and a receiver unit which receives light reflected off an optical disc; a signal processing unit which generates a main push-pull signal and sub push-pull signals from signals from the receiver unit, and obtains a signal obtained by subtracting the main push-pull signal from the sub push-pull signal multiplied K times, to generate a tracking-error signal; and a control unit which performs a midpoint servo process, an offset process of adding an offset value to a lens-error signal indicating displacement of the objective lens, a stabilization awaiting process of waiting for oscillation of the optical disc to stabilize, a measurement process of measuring the tracking-error signal, and a K value adjusting process of adjusting a value of K in response to a result of the measurement process.